The present invention relates to a tube for a heat exchanger, which is produced by forming beads on a brazing sheet for composing the tube and brazing the tops of the beads with the opposing portions in a tube part.
A conventionally known heat exchanger is configured by connecting a plurality of tubes for exchanging the heat of a medium so to communicate with header pipes for distributing and collecting the medium.
The tube used for such a type of heat exchanger is produced by forming a brazing sheet into the shape of a tube and brazing required points of the tube. The brazing sheet is formed by rolling, pressing or the like.
The brazing sheet has the surface of a plate matrix clad with a brazing material. Brazing is generally carried out by assembling tubes, header pipes and other members into one body and thermally treating the assembly. In other words, the required parts of the tube and other required parts of the heat exchanger are brazed by a single operation of heat treatment.
And, this tube is provided at appropriate intervals with beads for dividing passages for a medium. Specifically, the beads are formed by bending the brazing sheet so to have recessed portions, and the tops of the beads are brazed with the opposed portions within the tube part in order to improve the pressure resistance and heat-exchanging property of the tube.
For example, FIG. 9 is a transverse sectional view showing an example of forming the brazing sheet. FIGS. 10 and 11 are transverse sectional views each showing the top of a bead formed on the brazing sheet and the opposed portion within the tube part.
A brazing sheet B is provided with a plurality of beads 31, 31 at appropriate intervals and joint sections 32, 32 at both ends of the brazing sheet in its breadth direction. The brazing sheet B is folded along a folding section 33 at the center in the breadth direction so to join the joint sections 32, 32 mutually (see FIG. 9).
The formed body of the brazing sheet B is integrally assembled with other members and thermally treated so to braze the joint sections 32, 32 mutually.
When the brazing sheet B is folded, each of the beads 31 has its top 31a contacted to an opposed portion within a tube part 30 (see FIG. 10). The top 31a of the bead 31 is brazed with the opposed portion within the tube part 30 when the joint sections 32, 32 are mutually brazed (see FIG. 11). FIGS. 10 and 11 show that a brazing material 36 melts from the surface of a matrix 35 of the brazing sheet B to enter a space between the top 31a of the bead 31 and the opposed portion within the tube.
Arrows t in FIGS. 10 and 11 indicate a predetermined thickness of the tube 3. In other words, the matrix 35 of the brazing sheet B is determined so to have a predetermined dimension when the brazing sheet B is folded.
In order to secure the aforesaid satisfactory pressure resistance and heat-exchanging property for the tube for a heat exchanger, it is necessary to securely and firmly braze the tops of the beads with the opposed portions within the tube part.
The brazing between the tops of the beads and the opposed portions within the tube part is quite delicate to securely have the brazing material between them. Therefore, there was often a problem that brazing was defective at some positions in the tube.
For example, even when the tops of the beads are brought into contact with the opposed portions within the tube part in the stage of forming the brazing sheet into the tube part, the brazing material melts from the surface of the matrix 35 of the brazing sheet while brazing, and a space s corresponding to a thickness of the brazing material layer is formed between the tops 31a of the beads 31 and the opposed portions within the tube part as shown in FIG. 12. The space s formed between both sections of the matrix 35 makes it difficult to secure the brazing material needed for brazing and causes the degradation of a brazing property.
In view of the problems described above, it is an object of the present invention to provide a tube for a heat exchanger, which can have tops of beads brazed securely and firmly with opposed portions within a tube part, and a method for manufacturing the same.
According to the invention there is provided a tube for a heat exchanger having beads formed on a brazing sheet for configuring the tube and the tops of the beads brazed with opposed portions within a tube part, wherein the tops of the beads are crushed against the opposed portions within the tube.
According to the tube for a heat exchanger of the present invention, the tops of the beads are crushed in the opposed portions within the tube part, so that the tops of the beads can be brazed securely and firmly with the opposed portions within the tube part by virtue of the brazed portions.